The invention relates to a solvent and acid resistant membrane on the basis of polyacrylonitrile (PAN) and a comonomer copolymerized therewith, wherein the membrane is formed from the solution by phase inversion in water and also to a method of manufacturing the membrane.
In continuous processes using catalysts, such active compounds which, initiate strong interaction forces, are often immobilized on carrier materials such as membranes. This will be explained below in greater detail on the basis of the immobilization of enzymes.
Such an immobilization is appropriate and desired if:
1. The pH value changes drastically during the reaction and the reaction products formed can be rapidly removed from the ambient of the enzyme. PA1 2. The products formed in the medium employed, for example in the aqueous medium, need to be transferred constantly to another solvent, for example, an organic solvent in order to insure operation of the continuous process. PA1 3. The product and enzyme molecules have similar hydrodynamic diameters and therefore cannot be separated continuously by the separation processes usually employed.
If the enzymatic process is influenced furthermore with regard to a particular product composition while observing the process parameters mentioned above, then this is only possible if the reactors generally used (V&gt;100 ml) are reduced in sizes by an order of magnitude.
The pores of the membranes (V.about.1 .mu.l) can be considered to be microreactors in which the enzymes desired for performing the process can be covalently immobilized. For a well defined process procedure, the substrates can then be brought, by convention, close to the enzyme molecules immobilized in the pores. The micro-environment for the enzyme molecules can easily be controlled in this way by sensitive reactions.
With such membranes, the desired continuous process requires that a gradual development of bacteria in the whole reaction system is prevented. Membranes suitable for such a continuous process have been sterilized so far mainly by exposure to ethylene oxide gas, by treatment with secondary plasma or by various chemical disinfectants (PDI, Handbook Series: The Effect of Sterilization Methods on Plastics and Elastomers, Rapra Technology Ltd, Shawbury, Shrewsbury, Shropshire SY4 4NR UK 1994).
Particularly in the medical field, it is generally required that, for materials which may end up in the human body, no sterilization processes are used which may result in chemical alterations of the goods to be treated. Such a result, however, cannot be guaranteed with irradiation processes presently in use and, of course, not with chemical disinfections. With an exposure to ethylene oxide, there is the risk that, after the sterilization procedure, the gas cannot be fully removed.
Besides these well known sterilization processes which however include some risks, the hot steam sterilization in an autoclave is the safest method. All glass and hose materials and all metal parts can be sterilized in this way without problems. The superheated steam sterilization can furthermore be used universally with available apparatus and is therefore the most favored procedure. However, superheated steam sterilization detrimentally affects the membranes available so far. This is particularly true for membranes with reactive groups on their surfaces, which are present for the covalent bonding of enzyme molecules. Such membranes lose their reactivity during superheated steam sterilization.
It is the object of the present invention to provide a solvent-, acid- and heat-resistant membrane on which particularly catalysts can be immobilized.